Brass Compression Fittings For Flexible Polyethylene Tube

Compression fittings use three or four components per fitting to put pressure on the tubing's O.D. (outer diameter) to create a secure seal. Compression fittings are manually installed with wrenches and are commonly used in applications involving fluids, air, or certain gases (depending on the application, they are available in various metals or plastics, as well as well for various certifications). Compression fittings have been around for decades, and in recent years there has been a surgence towards newer "push-in" or "push to connect" style fittings which are more quickly installed.
Compression style fitting offers good flow characteristics because the interior of the tubing is unencumbered by inserts such as barbs. They are also compact and shorter in length compared to insert style fittings. Depending on the application and materials involved (plastic, metal), the fittings may be reused.
Compression fittings consist of a fitting body, an outer compression nut, an inner compression ring or ferrule, and in some cases an additional inner gripper. When the nut is tightened onto the fitting body, the ferrule compresses around the O.D. of the tubing creating a secure seal. The nut should be finger tightened, and then further tightened one additional turn using a wrench. It is important to avoid over-tightening, as the ferrule may deform and cause the seal to fail.